In the process of printing masks for semiconductor manufacturing, it is generally necessary to use the OPC technology to correct mask-board patterns. The formation of images with OPC-corrected mask boards can enable the target pattern formed on the semiconductor substrate to meet the target requirements, and can eliminate the distortion or deformation in the target pattern arising from the optical proximity effect.
The OPC verification is required for OPC-corrected mask boards before they are published so as to simulate whether the OPC-corrected masks are correct. In the existing first type of OPC verification method, verification results are generally based on the name sorting of design cells.
As the size of the chip increases, the repetitive structures in different cells increase, and the repetitive structures in different positions of the same cell also increase. This results in repetitive occurrence of similar verification results. Over a dozen types of structures may repeatedly occur for over a thousand times in a relevant verification report, which results in difficulties of screening problems.
Although the above-mentioned circumstances can be avoided in the existing second type of OPC verification method based on patterning, the following problems still exist.
1. It is difficult for the second type of OPC verification method to distinguish the rotation or mirroring in patterns. As shown in FIG. 1A and FIG. 1B, FIG. 1B is merely a pattern generated by a 90-degree clockwise turning of FIG. 1A; the verification results of FIG. 1A and FIG. 1B should be identical. However, the second type of OPC verification method will verify these two patterns separately and obtain respective verification results.
2. There are often subtle differences between OPC patterns, but it is difficult for the existing second type of OPC verification method to distinguish these kind of subtle differences therein. As shown in FIG. 1A and FIG. 1C, these two patterns are similar to each other, and there are only subtle differences in the corners thereof, which will not affect the results of OPC verification. However, the second type of OPC verification method will still verify these two patterns separately and arrive at their verification results, respectively.
Therefore, the existing second type of OPC verification method is unable to distinguish the rotation or mirroring in patterns as well as subtle differences therein, which results in difficulties in screening problems with the increase of the number of verification results.